Enhancement of MHC class I binding and immunogenic properties of the CTL epitope peptides derived from dengue virus NS3 protein by anchor residue replacement

ABSTRACT

The immunogenecity of the defined H-2Kd-restricted, murine cytotoxic T lymphocyte (CTL) epitopesof dengue viruses were examined for CTL induction in epitope peptide / H-2Kd tetramer assays. Thepeptides used in the study included those corresponding to amino acid (a.a.) residues 298-306(GYISTRVEM) of NS3 of dengue virus types 2 and 4 (named DENV-2/4), and to a.a. residues 299-307(GYISTRVGM) of NS3 of dengue virus types 1 and 3 (named DENV-1/3), and their respective modified epitope peptides, DENV-2/4-9L (GYISTRVEL) and DENV-1/3-9L (GYISTRVGL), in which the C-terminalresidue M of the original epitope peptide was replaced by L, in order to provide the complete H-2Kd-binding motif. Immunization of BALB/c mice with the original epitope peptide, DENV-2/4 or DENV-1/3, did not induce specific CTLs, while that with the modified epitope peptide, DENV-2/4-9L or DENV-1/3-9L, induced epitope peptide/H-2Kd tetramer-binding CD8+ cells indicating specific CTLs.Competition-based binding assay with biotinylated epitope-related reference peptides (DENV-2/4-9L-Biotin and DENV-1/3-9L-Biotin) demonstrated that the modified epitope peptide, DENV-2/4-9L and DENV-1/3-9L, had higher avidity to H-2Kd than the respective original epitope peptides. These results indicate that modification of dengue virus-derived CTL epitope peptide by replacing a.a. residue at theposition of anchor residue increases the binding avidity to MHC class I, resulting in the induction ofspecific CTLs. The strategy to enhance the immunogenicity of CTL epitope peptide may contribute to investigation of CTL biology in dengue virus infection.